Ship's Fresh Water Generator (Distillation Plant) | Starting and Stopping Procedures | Chief MAKOi

Summary

This video offers an in-depth look at the operation of a distillation plant aboard cargo ships, crucial for converting seawater into fresh water. It outlines the start-up and shutdown procedures, emphasizing the importance of the main engine's jacket water outlet as a heat source. The video explains the role of the ejector pump in creating a vacuum for boiling seawater at lower temperatures, the heat exchange process in the evaporator, and the collection of distilled water in the condenser. It also covers the critical steps of monitoring salinity with a salinometer and the disposal of non-evaporated seawater, ensuring the plant's efficient and safe operation.

Takeaways

• 🚢 Ocean-going ships use freshwater generators or desalination plants to convert seawater into fresh water due to the limited usability of seawater.
• 💧 The most common method for cargo ships is distillation, which requires the main engine to be running at navigation full speed.
• 🔥 The heating medium for distillation plants typically comes from the main engine's jacket water outlet, which is around 85-90 degrees Celsius.
• 🌊 It's important for ships to be in deep water and far from land to ensure the seawater used is clean and free of pollutants.
• 📦 The distillation process involves drawing seawater, creating a vacuum with an ejector pump, and heating the water to evaporate it in the evaporator.
• 🌡️ The boiling point of seawater is lowered inside the evaporator due to the vacuum created, allowing it to evaporate at temperatures below 100 degrees Celsius.
• 💧 The steam from the evaporator is condensed back into fresh water in the condenser, which is then collected and stored.
• 🔍 A salinometer is used to measure the salinity of the distilled water, ensuring it meets the required standards before being stored.
• 🚫 If the salinity is too high, an alarm is triggered, and the water is returned to the system to prevent contamination of the fresh water storage.
• 🛑 The shutdown process of the distillation plant is the reverse of the startup, ensuring the system cools down to prevent salt and scale buildup.

Q & A

Why do ocean-going ships need a freshwater generator?

Ocean-going ships need a freshwater generator because seawater, despite being abundant, has high salinity which makes it unsuitable for most shipboard operations and human requirements.

What are the two main methods used to convert seawater into fresh water on ships?

The two main methods used to convert seawater into fresh water on ships are distillation and reverse osmosis.

Which type of desalination plant is most commonly used on cargo ships?

The most commonly used type of desalination plant on cargo ships is the distillation plant.

What is the source of heating for the distillation plant on most ships?

The source of heating for the distillation plant on most ships is the jacket water outlet of the main engine, which typically has a temperature range between 85 to 90 degrees Celsius.

Why should the ship be far from land and in deep water when operating the distillation plant?

The ship should be far from land and in deep water to ensure that the seawater drawn into the distillation plant is clean and free of pollutants.

What is the role of the ejector pump in the distillation process?

The ejector pump creates a venturi effect, generating suction that helps maintain a vacuum inside the shell, which is necessary for the evaporation process to occur at lower temperatures than the boiling point of seawater.

How does the feed water line contribute to the efficiency of the distillation plant?

The feed water line draws seawater from the upper part of the condenser, preheating the feed water and improving the efficiency of the distillation process.

What is the purpose of the salinometer in the distillation plant?

The salinometer measures the salinity of the distilled water. If the salinity is higher than the set limit, an alarm is triggered, and the water is returned to the shell to prevent contaminated water from entering the freshwater storage tanks.

What happens to the salt that is not evaporated during the distillation process?

The salt remains dissolved in the seawater that hasn't evaporated and is suctioned by the inductor and pumped out into the sea as part of the continuous flow system.

What is the procedure to stop the distillation plant before the ship arrives in port?

The procedure to stop the distillation plant before the ship arrives in port involves switching off the dosing pump and salinometer, stopping the flow of heating into the evaporator, allowing the evaporator to cool down, stopping the ejector pump, closing all relevant valves, and opening the vacuum breaker.

Outlines

00:00

🚢 Starting and Stopping Procedures of a Ship's Distillation Plant

This paragraph explains the process of operating a freshwater generator, or desalination plant, aboard ocean-going ships. The freshwater generator is essential due to seawater's high salinity, which limits its use on ships. The most common type for cargo ships is the distillation plant, which converts seawater into fresh water by removing salt through distillation or reverse osmosis. The video will demonstrate the starting and stopping procedures of this plant. Distillation plants require the main engine to be running at full speed to operate, utilizing the engine's jacket water outlet as a heating medium. The starting procedure involves aligning the seawater line, opening various valves, and starting the ejector pump, which creates a vacuum effect to draw in seawater. The feed water line then introduces preheated seawater into the evaporator, where heat exchange occurs, and the process of converting seawater to fresh water begins.

05:14

🌡️ The Distillation Process and Salinity Control

This section delves into the distillation process, explaining how the feed water's temperature increases due to the heating medium from the main engine. Seawater's boiling point is slightly higher than pure water's due to its salinity, but the vacuum created by the ejector pump lowers the boiling point, allowing evaporation. The steam produced rises to the condenser, where it cools and condenses into distilled water. This water is collected and passed through a salinometer to ensure its salinity is below 5 ppm before being sent to the freshwater storage tank. The paragraph also addresses what happens to the salt left behind in the non-evaporated seawater, which is pumped out into the sea. In case of a malfunction or if the salinometer is switched off, a solenoid valve prevents untested water from entering the storage tanks. The video also touches on the continuous flow system and the importance of water treatment dosing pumps.

10:25

🛑 Safe Shutdown of the Distillation Plant

The final paragraph outlines the procedure for safely shutting down the distillation plant before the ship arrives in port. This involves turning off the dosing pump and salinometer, stopping the flow of heat to the evaporator, and allowing the evaporator to cool down to prevent salt and scale buildup. The shutdown process is essentially the reverse of the startup, with additional steps like closing the feed water valve, the condenser inlet and outlet valves, and the ejector pump inlet valve. A vacuum breaker is opened, and the ejector pump overboard valve is closed to complete the shutdown. If the ship is expected to stay in port for more than a day, it's recommended to drain the remaining feed water from the evaporator to maintain the plant's integrity.

Keywords

💡Freshwater Generator

A freshwater generator, also known as a desalination plant, is a critical piece of equipment on ocean-going ships. It is designed to convert seawater into fresh water by significantly reducing its salinity. This is essential for shipboard operations and human requirements, as seawater's high salinity makes it unsuitable for most uses. The video script describes how the freshwater generator operates, highlighting its importance in the context of a ship's freshwater supply.

💡Desalination

Desalination is the process of removing salt and other minerals from seawater to make it suitable for human consumption and other uses. The video script explains that desalination is achieved either through distillation or reverse osmosis. In the context of the video, distillation is the method used on cargo ships, which involves heating seawater to produce steam that is then condensed back into liquid form, leaving the salt behind.

💡Distillation Plant

A distillation plant is a type of desalination system that uses heat to separate salt from seawater. The video script details the operation of a distillation plant aboard a ship, where seawater is heated until it evaporates, leaving the salt behind, and the steam is then condensed into fresh water. This process is central to the video's demonstration of how ships produce their own freshwater supply.

💡Ejector Pump

An ejector pump is a type of centrifugal pump used in the distillation process to create a vacuum. The script describes how the ejector pump operates by using the venturi effect to draw in seawater, which is then heated and evaporated. The ejector pump plays a crucial role in maintaining the vacuum necessary for the efficient operation of the distillation plant.

💡Venturi Effect

The venturi effect refers to the decrease in fluid pressure that occurs when a fluid flows through a constricted section of a pipe. In the context of the video, the venturi effect is utilized by the ejector pump to create suction, which helps draw in seawater and maintain the necessary vacuum for the distillation process.

💡Condenser

A condenser in the context of a distillation plant is a heat exchanger that cools the steam produced from the evaporator, causing it to condense back into liquid form. The script explains that the condenser is part of the system that turns seawater into fresh water by cooling the steam and collecting the distilled water.

💡Evaporator

An evaporator is a component of the distillation plant where the actual separation of water from salt occurs. The script describes how seawater is heated in the evaporator, causing it to boil and produce steam, which is then condensed into fresh water in the condenser. The evaporator is a key part of the desalination process shown in the video.

💡Salinometer

A salinometer is a device used to measure the salinity of water. In the video script, the salinometer is mentioned as a critical component that ensures the freshwater produced meets the required salinity standards. If the salinity is too high, an alarm is triggered, and the water is redirected back into the system, ensuring only freshwater is stored.

💡Boiling Point

The boiling point is the temperature at which a liquid turns into vapor. The video script discusses how the boiling point of seawater is affected by the vacuum created by the ejector pump, which lowers the boiling point and facilitates the evaporation process in the distillation plant.

💡Combination Gas Law

The combination gas law is a principle in physics that relates the pressure, volume, and temperature of a gas. The script briefly mentions the combination gas law in the context of explaining how the pressure inside the distillation plant's shell is maintained below atmospheric pressure, which is crucial for the boiling and evaporation of seawater.

💡Treatment Dosing Pump

A treatment dosing pump is used to add chemicals to the freshwater to ensure it is safe for consumption. The video script indicates that once the freshwater production is stable, the treatment dosing pump is activated. This step is part of the final process to prepare the water for storage and use on the ship.

Highlights

Seawater's high salinity limits its use on ships, necessitating freshwater generators.

Desalination plants convert seawater to fresh water through distillation or reverse osmosis.

Distillation plants are commonly used on cargo ships for freshwater production.

Operation of distillation plants requires the main engine to be running at full speed.

Heating medium for distillation comes from the main engine's jacket water outlet.

Ships should be in deep water and far from land for clean seawater intake.

The ejector pump creates a vacuum for seawater intake through the adductor's venturi effect.

Feed water line draws preheated seawater from the upper part of the condenser.

Evaporator tubes facilitate heat exchange with the heating medium.

The boiling point of seawater is lowered due to the vacuum created by the ejector pump.

Steam from the evaporator rises to the condenser, cooling and condensing into distilled water.

Distillate pump transfers distilled water from the condenser to the freshwater storage tank.

Salinometer measures salinity, ensuring water quality before storage.

Salt remains in the non-evaporated seawater, which is pumped out into the sea.

Distillation plant operation includes a treatment dosing pump for water quality.

Distillation plant must be stopped before the ship arrives in port and the main engine slows down.

Evaporator cooling is crucial to prevent salt and scale buildup.

Vacuum breaker is opened, and the ejector pump overboard valve is closed to stop the plant.

Draining the evaporator is recommended if the ship stays in port for more than a day.

Transcripts

ocean-going ships are always surrounded

by water

but ironically apart from being a steady

supply of cooling medium

seawater has very limited uses when it

comes to shipboard operations and human

requirements due to its high salinity

which is why ships are equipped with

what is called a freshwater generator

or a desalination plant

which is a machine that drastically

lowers the salinity of seawater

in simple terms it converts seawater

into fresh water by removing the salt

either through distillation or reverse

osmosis

for cargo ships the most commonly used

type is the distillation plan

and in this video you will see both the

starting and stopping procedures

for most ships distillation plants can

only be operated when the main engine is

running at navigation full speed

this is because the heating medium it

uses comes from the jacket water outlet

of the main engine

which typically has a temperature range

between 85 to 90 degrees celsius

although there are some distillation

plant designs which can also use steam

from the boiler as the heating medium

it is recommended that the ship should

be far enough from land and in an area

with deep water to ensure that the sea

water that will go into the distillate

plant

will be clean and potentially be free of

pollutants

you may recall that i have made a

previous video about the operating

principles of the distillation plant

here in this video i'll be showing you

the actual operating procedures

the first step is to line up the sea

water line and open the valves starting

from the ejector overboard valve

next is the seawater inlet valve to the

ejector pump

and then the condenser inlet and outlet

valves

these lines draw seawater from the main

seawater line coming from the sea chest

once the ejector and condenser lines are

established the ejector pump can now be

started

the ejector pump is basically just a

centrifugal pump

which delivers seawater through an

inductor

the velocity of the seawater passing

through the nozzle in the adductor

creates a venturi effect which then

generates suction in this line

this continuous suction causes the

pressure inside the shell to become

lower than atmospheric pressure or in

simple terms a vacuum

the next step is to let seawater

into the distillation plant

this feed water line draws seawater from

the upper part of the condenser

which in effect makes the feed water

preheated

once the valve is opened the feed water

enters from the bottom and into the

evaporator which is basically a series

of tubes encased in a compartment

where the heating medium flows thereby

facilitating heat exchange

here we can see the sea water flowing

from the evaporator

remember the doctor line

the seawater and any other particles

gets suctioned through this line and

gets ejected out into the sea

now that we have established a

continuous flow of feed water we have

good vacuum inside the shell

and a continuous flow of cooling sea

water through the condenser

it's time to heat things up

by diverting the flow of the main engine

jacket water outlet into the evaporator

as you can see he's doing it slowly so

it's not to cause sudden fluctuations in

the jacket water line pressure

once the evaporator heating is lined up

the temperature will start to rise

and we can observe the feed water

reacting to the increase in temperature

as we all know pure water has a boiling

point of 100 degrees celsius at

atmospheric pressure

seawater's boiling point will be

slightly higher

now as i mentioned earlier the jagged

water temperature is around 85 to 90

degrees celsius

under normal atmospheric pressure

that won't be enough to evaporate

seawater

but thanks to the ejector pump and the

adductor

the pressure inside the shell is

maintained below atmospheric in effect

the lower atmospheric pressure causes

the boiling point of the seawater to

also become lower

i won't bore you with the mathematical

details but if you want to learn more

about this a good starting point would

be the combination gas law which is

derived from boyle's law charles lowe

and gay lucex law

now since the feed water is already

boiling the steam rises up to the

condenser where it is cooled down and

condenses into distilled water

there is a water collecting tray just

beneath the condenser tubes and it leads

down to this pipe which is the suction

line of the distillate pump

the distillate pump delivers the

distilled water from the condenser to

the fresh water storage tank

but before it does the water needs to

pass through the salinometer which

measures its salinity

the alarm is usually set to 5 ppm if the

salinity is higher than that

an alarm is triggered and the solenoid

valve automatically opens and returns

the distilled water back into the shell

during startup it is normal for the

salinity to be high during the first few

minutes but eventually it will go down

to the required value

and distilled water will be delivered to

the freshwater storage tanks

if in case the salinometer malfunctions

or is switched off the solenoid valve

will remain open thereby preventing

untested water to go to the storage

tanks

in the previous video a lot of viewers

asked where does the salt go

as we have all seen this is a continuous

flow system meaning it never dries up

so the salt remains dissolved in the

seawater that hasn't evaporated

as soon as that sea water flows out of

the evaporator tubes and into the shell

it will be suctioned by the inductor and

pumped out into the sea

once fresh water production is stable

the last step is to switch on the

treatment dosing pump

for a detailed explanation of this water

treatment

you can check out this video

now the distillate plant needs to be

stopped before the ship arrives in port

specifically it needs to be stopped

before the main engine is slowed down

for maneuvering and while the ship is

still in deep water

it's basically just the reverse of

startup procedures but i still think

it's worth seeing it get done

first will be to switch off the dosing

pump and the salonometer

next will be to stop the flow of heating

into the evaporator

let the evaporator cool down thoroughly

this is to ensure that no more

evaporation will take place

in order to prevent salt and scale

buildup within the evaporator tubes

you can verify if it's sufficiently

cooled down if the evaporator

temperature is the same as the seawater

temperature

once cooled down

stop the ejector pump

close the feed water valve

close the condenser inlet and outlet

valves

and the ejector pump inlet valve

after that

open the vacuum breaker

finally close the ejector pump overboard

valve

additionally if the ship is expected to

stay in port for more than a day

it's good practice to drain the

remaining feed water in the evaporator

i hope you enjoyed the video and stay

tuned for the next one